Pulse timer



Nov. 23, 1965 R. s. WALTON PULSE TIMER 2 Sheets-Sheet 1 Filed Dec. 26,1962 Q24 (SW 2 4 G w 6 H 4 w 6 l [I T. U 0 4 WV 3 J m mm R H M im R E VW V3? 1 w a Q B 4 2 6 firz 2/:

FIGS

INVENTOR.

RICHARD S. WALTON ATTORNEYS N 1965 R. s. WALTON 3,218,793

PULSE TIMER Filed Dec. 26, 1962 2 Sheets-Sheet 2 V70 I F I65 INVENTOR.

70 RICHARD S. WALTON BY 76 L98 Jam M 44M A TTORNEYI-S' United StatesPatent 3,218,793 PULSE TIMER Richard S. Walton, Willow Street, Pa.,assignor to Hamiltori Watch Company, Lancaster, Pa., a corporation ofPennsylvania Filed Dec. 26, 1962, Ser. No. 246,897 17 Claims. (Cl.58-28) This invention relates to pulse timers and more particularly to amechanically synchronized electronic oscillator of the self-startingelectric watch or clock-type.

Various arrangements are known for mechanically controlling the outputof an oscillator. As is well known the accuracy of an electronicoscillator, particularly at relatively low frequencies, variessubstantially with both temperature and voltage changes. For thisreason, it has been proposed in the past to control the output of suchan oscillator through the use of a separate oscillatory system in theform of a watch or clock mechanism. The mechanical oscillator is not sosusceptible to fluctuations in output and the overall accuracy of theoscillator being substantially that of the mechanical movement issignificantly increased.

A serious disadvantage of prior constructions, particularly thoseinvolving horological mechanical movements, is the fact that, ingeneral, no simple and eflective selfstarting arrangement has beenprovided.

The present invention avoids these difliculties by providing anelectrical pulse timer having the accuracy of a mechanical movementwhich incorporates a simple and reliable self-starting feature. Thedevice of the present invention, if provided with an electrical output,may be used as a pulse timer, providing accurately spaced low repetitionrate pulses for use as a low frequency time base, particularly in thefrequency range of about 1 to 20 cycles per second. Conversely, thedevice of the present invention if incorporated in an electric clock maybe provided with a mechanical output (movement of the watch hands) andin this form is a highly accurate and reliable electric watch or clockthat is automatically self-starting.

It is, therefore, one object of the present invention to provide a novelpulse timer.

Another object of the present invention is to provide a highly accuratepulse source usable as a time base.

Another object of the present invention is to provide aself-synchronized relaxation oscillator.

Another object of the present invention is to provide an automaticself-starting electric Watch or clock.

Another object of the present invention is to provide a mechanicallysynchronized electronic oscillator.

These and further objects and advantages of the invention will be moreapparent upon reference to the following specification, claims andappended drawings wherein:

FIGURE 1 shows one embodiment of the present invention in the form ofthe self-synchronized relaxation oscillator.

FIGURE 2 shows a modified embodiment in the form of a mechanicallysynchronized oscillator usable either as a pulse source or as a watch orclock movement.

FIGURE 3 is a circuit diagram of a further modified embodiment of thepresent invention.

FIGURE 4 is an elevational view with parts in section showing a modifiedmechanical oscillatory system usable in the circuit of FIGURE 3.

FIGURE 5 is a plan view with parts broken away and parts in section ofthe mechanical oscillatory system of FIGURE 4; and

FIGURE 6 is a cross-section through the coils taken along line 6-6 ofFIGURE 4.

Referring to the drawings, FIGURE 1 shows a selfsynchronized oscillatorconstructed in accordance with the 'ice present invention, generallyindicated at 10 including a unijunction transistor 12 connected betweena positive power supply terminal 14 and negative or grounded terminal16. Unijunction transistors are well known and include an emitter 18 andtwo base contacts 20 and 22. Connected between the emitter 18 and thepositive supply 14 is a resistor 24. A capacitor 26 is connected betweenthe emitter 18 and the negative power supply terminal 16. A secondresistor 28 is connected between base contact 20 and the positive sideof the power supply, while a load resistor 30 is connected between theother base contact 22 and the negative terminal 16 of the power supply.

In order to provide self-synchronization, the output terminal 32 of theoscillator is connected through a time delay circuit 34 and an inverter36 to the base contact 20. In this way, a portion of the output pulsewaveform is fed back to the unijunction transistor 12. The delayinserted by delay element 34 is preferably slightly less than thenatural pulse spacing of the oscillator. The positive output pulsesappearing at output terminal 32 are inverted in invertor 36 and appliedas negative pulses to the base contact 20.

In operation, when DC. power is applied across terminals 14 and 16,capacitor 26 charges up and the potential of emitter 18 rises inaccordance with the RC time constant of the oscillator. When thepotential of emitter 18 reaches a predetermined value, transistor 12conducts and draws heavy current through resistor 30 both from emitter18 and from base contacts 20 and 22. The conduction of transistor 12causes capacitor 26 to discharge until the potential of the emitter 18drops below cutoff and the transistor 12 is cut off. This surge of heavycurrent through load resistor 30 appears as a positive pulse at outputterminal 32. After the transistor has turned off capacitor 26 begins torecharge in accordance with the natural time constant of the oscillator.

However, a portion of the output in the form of a positive pulse is fedto the time delay circuit 34 and invertor 36 to appear as a delayednegative pulse at base contact 20. The time delay of circuit 34 ispreferably chosen so that the negative pulse appears at contact 20before the transistor 12 is again turned on by the recharging capacitor26. The negative pulse applied to base contact 20 momentarily lowers thevoltage gradient along the base between contacts 20 and 22 so that thepotential of emitter 18 due to the potential across recharging capacitor26 is suflicient to again turn the transistor on. With the transistorturned on heavy current is again drawn through load resistor 30,capacitor 26 is again discharged and the entire cycle repeated. Theresultant output at terminal 32 is a series of positive pulses having arepetition rate governed by the time delay circuit 34.

It is apparent that the time delay inserted by circuit 34 is independentof the supply voltage across terminals 14 and 16 and if this circuit iscarefully selected to be substantially independent of temperature a veryaccurate pulse output spacing can be obtained suitable for use as a lowfrequency time base. The time delay device 34 may be any of the wellknown electrical or mechanical delay devices.

FIGURE 2 shows a modified embodiment wherein the time delay element 34takes the form of a mechanical balance of the type conventionallyemployed in an electric watch or clock. In FIGURE 2 like parts bear likereference numerals and the electronic oscillator portion of the devicegenerally indicated at 10 again includes the unijunction transistor 12in combination with the previously described relaxation oscillatorcircuit parameters. The load resistor takes the form of a semiconductordiode 38 connected to the output terminal 32 and the entire oscillatorcircuit is connected between a positive nine volt D.C. source andground.

Base contact is connected to the emitter 40 of a PNP junction transistor42, having a base 44 and collector 46. Collector 46 is connected to thenegative side of the power supply or ground while base 44 is connectedto one side of a resistor 48; the other side of which is likewiseconnected to the negative side of the power supply. Transistor 42 actsas an amplifier and pulse inverter.

The mechanical timing device 34 includes a generally U-shaped frame 50rotatably supporting a balance staff 52 upon which is mounted aconventional balance wheel 54. Balance staff 52 is connected to theusual hairspring 56 and the balance wheel receives through a suitableaperture in its rim a small permanent magnet 58.

Magnet 58 is provided at each end with poles to create a vertical fluxextending from the top and bottom edges of the balance wheel rim whichflux is periodically intercepted by the adjacent windings of a drivecoil 60 and pick up or trigger coil 62 positioned below and above thebalance wheel rim respectively. Drive coil 60 is connected by way ofleads 64 and 66 across output diode 38 while pickup coil 62 is connectedby way of leads 68 and '70 to the emitter and base respectively ofamplifier transistor 42.

In operation, when the voltage across capacitor 26 reaches a certainvalue as determined by the circuit parameters, the unijunctiontransistor 12 conducts, discharging the capacitor through the drive coil60. When the drive coil 60 is energized it creates a magnetic fieldwhich reacts with the field of permanent magnet 58 in the rim of thebalance wheel. This impulses the balance wheel and starts oscillation ofthe balance system. After capacitor 26 has discharged to a certainlevel, the unijunction transistor no longer conducts. When theunijunction transistor is not conducting capacitor 26 again begins tocharge at a rate determined primarily by resistor 24. As the balancewheel swings under the influence of hairspring 56 the magnet 58 passesthe trigger or pickup coil 62 and induces a voltage on that coil. Thisvoltage is fed to the base of transistor 42 which causes this transistorto conduct. When transistor 42 draws current between emitter 40 andcollector 46 it lowers the voltage gradient across contacts 20 and 22 ofthe unijunction transistor 12. This causes the unijunction transistor toconduct and when this transistor conducts it discharges capacitor 26through the drive coil 60 and again impulses the balance wheel. In thismanner, the frequency of the electronic network is determined by thefrequency of the balance wheel rather than by the combination ofresistor 24- and capacitor 26. A highly accurate pulse generator isobtained which is not dependent upon the characteristics of theelectrical circuit. The electronic oscillator circuit is used forstarting and as a fairly accurate secondary pulse source in the event offailure in the mechanical system.

It is apparent that the arrangement of FIGURE 2 can be used as a powersource for an electric watch where, instead of taking an output fromterminal 32, the output may be that of the watch or clock hands drivenin the conventional manner of an electric clock or watch from thebalance staff 52. In such a case, the electronic oscillator functions asa simplified and reliable self-starting power circuit for the electricwatch.

FIGURE 3 shows a circuit diagram for a modified device constructed inaccordance with the present invention with like parts again bearing likereference numerals. The mechanical portions of this embodiment are shownin FIGURES 4-6. The circuit of FIGURE 3 is similar to the electroniccircuit portion of the embodiment of FIGURE 2 with the exception of theelimination of output diode 38 and the incorporation of modified driveand trigger coils. In FIGURE 3 the trigger coil indicated by the dashbox at 70 is shown as having an inductance 72 and an internal resistance'74. Similarly, the drive coil in- 4 inductance 78 and an internalresistance 30. In some dicated by the dash line box 76 is illustrated ashaving an instances it may be desirable to provide the output through acoupling capacitor 33 and to provide a bias resistor 35 for thecollector of transistor 42.

FIGURES 4 through 6 show a mechanical timer usable with the electroniccircuit of FIGURE 3. The mechanical timer, again generally indicated bythe reference numeral 34 comprises a balance staff 82 rotatablyjournalled in suitable supports (not shown). Carried by the balancestaff is a conventional hairspring collet 84 coupled in a conventionalmanner to the hairspring 85 of a conventional electric watch movement.The balance staff may drive the hands of the watch through an index andgear train in a well known manner. Mounted on and rotatable with thebalance staff 82 is a generally U-shaped keeper 86 made of soft iron orother suitable material. Balance staff 82 also carries a balance wheel87 of non-magnetic material such as aluminum formed of two semi-circularsections 88 and 89. Joined to the ends of semi-circular sections 83 and39 is an elongated rectangular permanent magnet 91) having a centralaperture received over the balance staff 82. Keeper 86, balance wheel8'7 and permanent magnet are all rotatable with the balance staff 82.The adjacent ends of the balance wheel sections are spaced to receivethe opposite ends of the permanent magnet 99 which extend to the outeredges of the balance wheel.

Coils 70 and 76 are of bifilar wire and are simultaneously wound on acommon coil form in the shape of a closed generally rectangular loophaving short vertical sides 92 and 94 and longer horizontal sides 96 and98. As best seen in FIGURE 5, the longer sides 96 and 93 are both curvedin a gentle arc to provide clearance for the balance staff 82. Thedirection of the windings, i.e., current flow through these coils, inindicated by the arrows 100 in FIGURE 4. Coils 70 and 76 are providedwith terminals 102 and 104 for connection into the electrical circuit ofFIGURE 3.

With reference to the embodiment of FIGURES 3 through 6, the coils arefixed by a suitable support so that the balance wheel is placed suchthat the coil windings surround the balance wheel but not the shunt 86.This provides shielding for the hairspring connected to collet 84. Thevertical portions 92 and 94 of the coils lie in the air gaps labelled Aand B in FIGURE 4.

As the electronic circuitry energizes one of the coils, the currentflowing through this coil creates a magnetic field such that itinteracts with a magnetic field caused by the permanent magnet 90 incombination with magnetic shunt 86. This interaction causes the balancewheel and shunt to be pushed away from the coil. The interaction betweenthe two fields impulses the balance wheel assembly and therefore startsit oscillating. The circuit of FIG- URE 3 allows only a short momentarypulse in the drive coil and therefore the balance wheel is allowed topass the coils on its return swing without any impulse to the balancewheel. As the balance wheel completes one full oscillation, the coilsare again in the air gaps A and B. This time the movement of thepermanent magnet past one of the coils generates a voltage in this coiland therefore triggers the electrical circuit and allows current to flowin the drive coil. Again the interaction between the two magnetic fieldsimparts momentum to the balance and hairspring combination and therebysustains the mechanical oscillations.

Referring specifically to FIGURE 3, when the mechanical oscillator is atrest and nine volts DC. is impressed across the power supply terminals,the capacitor 26 charges at a rate determined by resistor 24. The timerequired for capacitor 26 to attain a voltage of 0.707 9 volts isdetermined by the time constant of elements 24 and 26. Also, when thenine volts is applied, this voltage is divided proportionally acrossresistor 28, unijunction transistor 12 and resistance 80. The ratio ofthese voltages is determined by the ratio of the resistances associatedwith each of these elements.

In a properly designed circuit of this type, the majority of the voltageis across the transistor 12. When the voltage across capacitor 26reaches approximately 70% of the voltage across transistor 12 andresistance 80, transistor 12 exhibits a negative resistancecharacteristic between emitter 18 and base contact 22. This allows thecapacitor to discharge through the emitter and base contact to resistor80 and drive coil 78. The current passing through coil 78 generates amagnetic field which repels the field of the permanent magnet on thebalance wheel, thus imparting momentum to the balance Wheel.

The charge continues to flow from capacitor 26 until the voltage acrossthe capacitor reaches a certain level at which time the transistor cutsoff and no longer exhibits a negative resistance characteristic. Thetime associated with the discharge of capacitor 26 is in theneighborhood of several milliseconds. When the transistor no longerexhibits negative resistance characteristics, capacitor 26 again beginsto charge by virtue of the current passing through resistor 24.

As the permanent magnet on the balance wheel swings past the triggercoil 70 it generates a voltage in this coil. This generated voltage isimpressed across terminals 40 and 44 of transistor 42 which forces thistransistor to exhibit negative resistance characteristics between itsemitter and collector. The resistor turns on and current flows from thenine volt source through resistor 28 and through 42 to ground. Themagnitude of the current flowing through these two elements isdetermined by the voltage generated in the trigger coil and thus thevoltage impressed across the terminals 40 and 44. The current flowingthrough resistor 28 due to the negative resistance characteristics ofthe amplifier transistor causes a higher than normal voltage drop acrossresistor 28 and thus lowers the voltage across unijunction transistor 12and resistor 80. When this action occurs, the voltage associated withthe charge on capacitor 26 becomes a higher percentage of the voltageacross the unijunction transistor and the unijunction transistor againexhibits negative resistance characteristics.

It can be seen that with the natural frequency of the electronicoscillator slightly lower than the natural frequency of the balance andhairspring combination, the action of the balance wheel passing thetrigger coil causes the electronic oscillator to oscillate at a higherfrequency than its natural frequency. Therefore, the electronicoscillator is synchronized with the mechanical oscillator. In this Way,it is possible to make the electronic oscillator oscillate at afrequency determined by the mechanical oscillator with an accuracy whichvery closely approaches the accuracy of the mechanical oscillator. Thisis desir able since the accuracy of the electronic oscillator alone isdependent upon temperature variations and voltage variations whereas themechanical oscillator is not nearly as susceptible to thesefluctuations.

It is apparent from the above that the present invention provides anovel self-synchronized oscillator usable either as a time base or as aself-starting power source for an electric clock or watch. A novelfeature of the present invention involves the synchronization of arelaxation oscillator by means of a more accurate time delay element,preferably in the form of a watch or a clock balance system. When usedas a pulse standard or time base, the output has substantially theaccuracy of the mechanical movement.

In every case the synchronization signal is applied to a separateelectrode of a unijunction transistor and is completely isolated fromthe natural control circuit of the relaxation oscillator. This assuresreliable self starting and permits operation of the electronic circuitas a secondary oscillator in the event of failure in the mechanicalsystem.

Thus, in addition to providing self-starting, the electrical oscillatorprovides a secondary oscillatory source which is effective to continueto give fairly accurately spaced output pulses even if something shouldhappen to cause breakdown of the mechanical system. Also provided is anovel arrangement for driving a balance system which substantiallyincreases the overall efiiciency of the unit.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. A timing device comprising a relaxation oscillator including a threeterminal impedance, a second impedance coupled to a first terminal ofsaid three terminal impedance for controlling the oscillations thereof,and time delay means for feeding a signal from a second terminal to athird terminal of said three terminal impedance.

2. A timing device comprising a. relaxation oscillator including aunijunction transistor having an emitter and a pair of base contacts,means for deriving a repetitive signal from said oscillator, and timedelay means for feeding said signal to one of the base contacts of saidtransistor.

3. A device according to claim 2 wherein said time delay means is amechanical timer.

4. A device according to claim 3 wherein said time delay means is thebalance system of an electric watch.

5. A timing device comprising a unijunction transistor having two baseelectrodes and a third electrode, means for connecting a power supplyacross said base electrodes, a capacitor coupled to said third electrodeof said transistor, a load impedance for said transistor, and time delaymeans for feeding a signal from said load impedance to one of said baseelectrodes of said transistor.

6. A timing device comprising a unijunction transistor having an emitterand two base contacts, means for coupling said transistor to a powersupply, an R-C control circuit coupled to said emitter, means forderiving a repetitive signal from the base circuit of said transistor,and time delay means for feeding said signal to one of said basecontacts.

7. A timing device comprising a unijunction transistor having an emitterand .a pair of base contacts, a pair of power supply terminals, aresistor coupling said emitter to one of said terminals, a capacitorcoupling said emitter to the other of said terminals, a load impedancecoupling one of said base contacts to one of said terminals, and timedelay means coupling said load impedance to the other of said basecontacts.

8. A device according to claim 7 including a pulse inverter in serieswith said time delay means.

9. A timing device comprising a unijunction transistor having an emitterand two base contacts, positive and negative power supply terminals, afirst resistor connected between said emitter and said positiveterminal, a capacitor connected between said emitter and said negativeterminal, a second resistor connected between one of said base contactsand said positive terminal, a third resistor connected between the otherof said base contacts and said negative terminal, and time delay meansand a pulse inverter connected in series between said base contacts.

10. A device according to claim 9 including an electrical outputterminal coupled to one of said base contacts.

11. A timing device comprising a unijunction transistor relaxationoscillator, a mechanical oscillatory system including impulse andtrigger coils, means coupling said impulse coil to one base contact ofsaid transistor, and means coupling said trigger coil to the other basecontact of said transistor.

12. A device according to claim 11 including amplifier means couplingsaid trigger coil to said other base contact.

13. A device according to claim 12 wherein said amplifier meanscomprises a junction transistor.

14. A timing device comprising a unijunction transistor relaxationoscillator, a mechanical oscillatory system including a balance wheel,magnetic means rotatable with said balance wheel, impulse and triggercoils located adjacent the path of movement of said magnetic means,means coupling said impulse coil to one base contact of said transistor,and means coupling said trigger coil to the other base contact of saidtransistor.

15. A timing device comprising a unijunction transistor relaxationoscillator, a junction transistor having its output coupled to one basecontact of said unijunction transistor, a mechanical oscillatory systemincluding a balance staff and balance wheel, a permanent magnet carriedby said balance staff, impulse and trigger coils positioned adjacent thepath of movement of said permanent magnet for periodically reacting withthe flux from said magnet, means coupling said impulse coil to the otherbase contact of said unijunction transistor, and

means coupling said trigger coil to the input of said junctiontransistor.

16. A device according to claim 15 wherein said permanent magnet ismounted transverse to said balance staff and a magnetic shunt is mountedon said balance staff having ends adjacent to but spaced from the endsof said permanent magnet.

17. A device according to claim 1 wherein said three terminal impedancehas negative resistance characteristics.

References Cited by the Examiner UNITED STATES PATENTS 3,005,305 10/1961Thoma 582l 3,026,485 3/1962 Suran 331-108 3,035,183 5/1962 Siebertz eta1 307-88.5 3,074,028 1/1963 Mammano 33l-11l 3,152,295 10/1964 Schebler318118 20 MILTON O. HIRSHFIELD, Primary Examiner.

JOSEPH A. STRIZAK, Examiner.

14. A TIMING DEVICE COMPRISING A UNIJUNCTION TRANSISTOR RELAXATIONOSCILLATOR, A MECHANICAL OSCILLATORY SYSTEM INCLUDING A BALANCE WHEEL,MAGNETIC MEANS ROTATABLE WITH SAID BALANCE WHEEL, IMPULSE AND TRIGGERCOILS LOCATED ADJACENT THE PATH OF MOVEMENT OF SAID MAGNETIC MEANS,MEANS COUPLING SAID IMPULSE COIL TO ONE BASE CONTACT OF SAID TRANSISTOR,AND MEANS COUPLING SAID TRIGGER COIL TO THE OTHER BASE CONTACT OF SAIDTRANSISTOR.